1. Field of the Invention
The present invention relates generally to a coating apparatus and, more particularly, to a coating apparatus for coating vehicle bodies which are conveyed continuously along a production line.
2. Description of Related Art
In a vehicle body coating line, a coating apparatus has been recently utilized for coating chipping paint including urethane paint on the lower side of a vehicle body.
Japanese Patent Publication 59-1107 discloses a painting gun for coating side sills located on vehicle side bodies conveyed successively along a production line. This spray gun moves in the opposite direction to the movement of the conveyed vehicle body, when it coats side sills, and returns to its initial position without spraying. This publication also discloses that the painting gun has two moving speeds, one when the conveyor is running and the other when the conveyor is stopped.
Another known coating method has been proposed which includes a reciprocating unit located beside a vehicle body conveyor. This reciprocating unit, carrying a plurality of spray guns, performs at least one reciprocating painting movement of the spray gun on each vehicle body. However, this conventional reciprocating unit sets a fixed or predetermined speed for the reciprocating movement. Accordingly, the relative speed between the vehicle body and the spray gun is inherently different in each stroke of reciprocating movement, and this difference in the relative speed is likely to cause unevenness in coating.